%I #5 Mar 30 2012 16:45:51
%S 1,1,3,8,22,68,216,728,2513,8920,32116,117240,431550,1600734,5970704,
%T 22381184,84236890,318191804,1205692236,4581481776,17452915218,
%U 66637798834,254960616136,977346581800,3753005281872
%N Number of CdI_2 polytypes that repeat after 2n layers.
%D T. J. McLarnan, The numbers of polytypes ..., Zeits. Krist. 155, 269-291 (1981).
%K nonn,easy
%O 1,3
%A _N. J. A. Sloane_.